In typical commercial electrographic reproduction apparatus (copier/duplicators, printers, or the like), a latent image charge pattern is formed on a uniformly charged charge-retentive or photoconductive member having dielectric characteristics (hereinafter referred to as the dielectric support member). Pigmented marking particles are attracted to the latent image charge pattern to develop such image on the dielectric support member. A receiver member, such as a sheet of paper, transparency or other medium, is then brought into contact with the dielectric support member, and an electric field applied to transfer the marking particle developed image to the receiver member from the dielectric support member. After transfer, the receiver member bearing the transferred image is transported away from the dielectric support member, and the image is fixed (fused) to the receiver member by heat and pressure to form a permanent reproduction thereon.
One type of development station commonly utilized in electrographic reproduction apparatus is the magnetic brush development station. The magnetic brush development station includes, a housing containing a plurality of elements and providing a reservoir for a supply of developer material. The developer material may be, for example, two-component material comprising magnetic carrier particles and relatively smaller pigmented marking particles. Included in the elements of the development station, a mixer assembly, such as a paddle wheel, auger or ribbon blender, is located in the reservoir and serves to stir the carrier particles and marking particles to triboelectrically charge the particles so that the marking particles adhere to the surface of the carrier particles. A transport mechanism brings the developer material from the reservoir into the field of a plurality of magnets within a rotating sleeve, commonly referred to as the toning roller (of course, the magnets could rotate and the sleeve remain stationary or rotate with a different angular velocity from the magnets). The rotating sleeve and magnetic fields cause the marking particles to be brought into the vicinity of the latent image charge patterns on the dielectric support member to be applied to the latent image charge patterns in order to develop such patterns (see, for example, U.S. Pat. No. 4,887,132, issued Dec. 12, 1989, in the names of Joseph, et al).
As will be appreciated, the respective drive shafts for the mixer assembly and transport mechanism of the electrographic reproduction apparatus development station run through the development station and are supported in bearings in the development station housing walls. While the bearings are generally protected by seals, due to the nature of the developer material, known seal arrangements have not been totally effective in protecting the bearings. The minute particle size of the development material enables the developer material to migrate through the seals into the bearings causing premature bearing life failure.